OTTAWA -- The Canadian Union of Postal Workers issued a request Saturday for the federal government to appoint a mediator in its contract talks with Canada Post, as it rejected the Crown corporation's latest offers.

Canada Post issued new, time sensitive, proposals last week aimed at reaching agreements with its approximately 42,000 urban employees and 8,000 rural and suburban carriers.

Prime Minister Justin Trudeau weighed in Saturday night with a last-minute plea to the two sides, just hours before the midnight deadline on the Crown corporation's offers expired. In a Twitter post, Trudeau cited the arrival of the holiday shopping season and urged both sides "to resolve their differences quickly and reach a deal."

But as the deadline on the offers passed, CUPW issued a statement that said it had responded "by presenting the Corporation with our own global offers that address our needs and demands."

The union also said that it had asked the government to appoint a mediator to help the two sides reach an accord after nearly a year of talks, adding "We believe that our proposals can be the basis of collective agreements."

CUPW had said on Friday that the new proposals from Canada Post made positive steps, but not enough to end the rotating strikes that have shut down postal operations in more than 200 communities, creating a huge backlog of undelivered mail. It said it would not bring the offers to a vote of its members, although both sides remained at the bargaining table.

On Saturday the Retail Council of Canada urged Ottawa to "bring an immediate end" to the rotating strikes through back-to-work legislation.

"Just as retail merchants, our workforce of two million and our customers enter the busiest time of year, the postal system is grinding to a near-halt," council president Diane Brisebois wrote in a letter to Trudeau.

Earlier in the week, eBay called on the government to legislate an end to the dispute in time for Black Friday and Cyber Monday sales events tied to the American Thanksgiving.

Trudeau said last week that "all options" would be on the table to end postal disruptions if there was no progress in bargaining.

A government source, speaking on condition of anonymity, said decisions on how to end the job action by postal workers could come as early as Sunday, adding that "'all the options' does include legislating."